Play it Forward Adventures specializes in tours which include volunteer work.

Example — a 15-day trip to Chile includes five days’ trekking through Cerro Castillo National Park and centers on teaching English to schoolchildren in Patagonian villages. The land cost of $3,195 includes in-country flights and transportation, lodging, meals, all materials for the volunteer project, outdoor activities and park fees.

Contact Play it Forward Adventures (Box 14126, St. Paul, MN 55114;...

Tourcaster.com offers 250 downloadable audio tours of more than 30 cities on six continents. They can be added to MP3 players, including iPods, or burned onto a CD. Most tours cost $5-$23 each, and each comes with a numbered map and detailed directions.

Example — the “Piazza del Popolo to Fontana di Trevi” tour of Rome takes 2½ hours, with an audio length of one hour nine minutes, and costs $19.90.

For many destinations in Europe, South America and Asia, the site offers 20- to...

One of the largest Norman castles still surviving now serves as a dormitory for students attending University College (Durham Castle, Palace Green, Durham, DH1 3RW, U.K.; phone 0191 334 3800, fax 0191 334 3801, www.dur.ac.uk/university.college).

Guided tours of the castle are offered each afternoon from Easter to Sept. 30 and on Monday, Wednesday, Saturday and Sunday for all other dates. Tours may be canceled for school events; check with the castle porter (phone 0191 334 3800) before...